The Hamiltonian () is still physically equal to the exact Hamiltonian of irradiated exciton (REF ). To proceed within the conventional Floquet theory, one can apply the \(1/\omega _0\)  expansion (the Floquet-Magnus expansion [1]}, [2]}, [3]}, [4]}) in order to turn the periodically time-dependent Hamiltonian () into the effective stationary Hamiltonian with the main term
\(\hat{\cal H}_{\mathrm {eff}}=\hat{\cal H}_{0},\) 
